1. Field of the Invention
The present invention relates to a motor control device for electric vehicles comprising a motor transmission system that transmits power from an electric motor to the drive wheels, such as electric cars equipped with only an electric motor as the motor or a hybrid vehicle equipped with an electric motor and an engine as the motor.
2. Background Information
Conventionally, as an electric vehicle, such as that disclosed in Japanese Laid-Open Patent Publication No. 1993-176419, which interposes an automatic transmission (a continuously variable transmission) in the above-described motor transmission system and transmits power from an electric motor to the drive wheels via this automatic transmission (a continuously variable transmission) is known.
Additionally, Japanese Laid-Open Patent Publication No. 1993-176419 further discloses a motor control technology in which, upon controlling the rotational speed of an electric motor via a shift control of the automatic transmission (a continuously variable transmission) in a manner in which the efficiency of the motor and the inverter that is in charge of the motor is maximized, that is, in a manner so that the power consumption rate (the power cost) is optimal, a target motor rotational speed that can achieve the required driving power is calculated, and the automatic transmission (a continuously variable transmission) is shifted to a target gear ratio that matches the actual rotational speed of the electric motor to this target motor rotational speed.